The present invention relates to telescoping columns and, more particularly, to self-locking mechanisms for telescoping columns.
Telescoping columns typically include two or more tubes arranged in telescoping fashion. That is, one or more tubes are aligned along a common centerline, with each tube in the column being received within a preceding tube in the column. The column can be extended, where each tube is partially withdrawn from its preceding tube, and contracted, where each tube is fully or partially inserted within its preceding tube, as in a telescope.
Telescoping columns are used in a variety of applications. For example, telescoping columns are used in motor vehicles to absorb impact forces. One application of a telescoping column in a motor vehicle is in an extendible bumper system. Another application of a telescoping column in a motor vehicle is in a passenger restraint system.
Extendible bumper systems include one or more telescoping columns that support a front or rear bumper structure. The telescoping column is extended and retracted to move the bumper structure. Typically, these systems support the bumper structure close to the body of the motor vehicle during certain conditions, such as when the vehicle is being parked, and extend the bumper structure from the body during other conditions to increase the ability of the telescoping columns to convert the kinetic energy of a force on the bumper structure into work.
Passenger restraint systems may also include a telescoping column for extending and retracting a restraint structure. During certain conditions, these systems support the restraint structure in a position that allows freedom of passenger movement. In other conditions, these systems extend the restraint structure to restrain passenger movement and absorb the kinetic energy of a force on the restraint structure. One example of such a passenger restraint system is an extendible and retractable knee bolster system.
Where a telescoping column is to be used to absorb an impact force, the column may be fitted with a resistance medium between tubes in the column. The resistance medium provides little or no resistance to the movement of the movable structural elements relative to the fixed structural elements when the bumper is being extended or retracted by the actuator. In response to an impact force, however, the resistance medium “locks”, providing an increased resistance to the relative movement of the tubes to convert the kinetic energy of the force into work. Accordingly, the resistance medium in a telescoping column is known as a self-locking mechanism.